The present invention relates to graphical displays for apparatus, for example control units for medical equipment such as units far administration of continuous positive airway pressure (CPAP) to a patient having means for display of information generated by operation of the apparatus.
In electrically operated apparatus, it may be desired to display status information on the housing of the apparatus in order to facilitate user operation. In its simplest form, such information may be displayed by a single light emitting diode (LED) which lights up or flashes in a particular sequence to convey the information. An example of this is flashing of an LED to indicate the number of messages on a telephone answering machine. Using a single LED limits the amount of information which may be conveyed or, to increase the amount of information, the manufacturer must resort to cryptic codes which are difficult for the user to remember.
More information can be displayed by toe of an array of LEDs or a liquid crystal display (LCD), which may be arranged in the familiar 7-segment display commonly used to reproduce alphanumeric characters in Roman script.
Known types of graphical displays include LCDs, multi-segment LEDs and surface-mounted LEDs, the latter having a matrix of LEDs mounted directly to the surface of a printed circuit board (PCB).
The surface-mounted LEDs have advantages over LCDs, and multi-segment LEDs both in terms of lower component costs and facility for automated assembly, and thus, for large scale manufacture, lowest assembly cost. However, surface-mounted LEDs have the disadvantage of being difficult to read unless mounted close to the surface of the apparatus housing. An example of this may be seen in U.S. Pat. No. 5,703,625 to Snider et al.
Snider et al provides translucent buttons and an adjacent display lens in front of a graphical display device such as an LCD or LED array. The common graphical display device is employed to provide both fixed images displayed through the buttons to indicate their function and variable information indicating the status of the system through the lens.
The present invention seeks to provide a low-cost alternative to the prior art.
In a first form, the present invention provides, in electrically operated apparatus, a graphical display capable of displaying information generated by operation of the apparatus, including a printed circuit board, a plurality of surface-mounted light emitting diodes arranged in a matrix on the surface of the printed circuit board, means for selectively illuminating said light emitting diodes in response to information generated by operation of the apparatus, display means including a light transmitting display surface and a plurality of elongate light conduit means for transmitting light from a respective portion of said matrix of fight emitting diodes to a portion of said display surface, such that said information generated by operation of the apparatus is displayed graphically by said display surface.
Preferably, the display means includes a respective light conduit means for each of the light emitting diodes. Preferably also, the graphical display on the display surface is arranged in a like matrix to The matrix of light emitting diodes.
Preferably, the light conduit means are integrally formed with the display means and, most preferably, are integrally moulded with the display surface.
In a further form of the invention, the display surface is included in a switch operating member of an electrical switch of the apparatus. Preferably, the apparatus further includes means responding to switch operation to cause display of said information by said switch.
Preferably the apparatus includes a plurality of such switches, and the results of the operation of one or more such switches are displayed by another such switch or switches.
Preferably the graphical display means far each switch includes a plurality of said light emitting diodes individually controllable for the generation of images such as letters, numerals or symbols or combinations thereof.